As a rule, a processing apparatus for photographic sheet material comprises several vessels each of which contains a treatment liquid, such as a developer, a fixer and a rinse liquid. As used herein, the term sheet material includes not only photographic material in the form of cut sheets, but also in the form of a web unwound from a roll. The sheet material to be processed is transported through these vessels in turn, by transport means such as one or more pairs of drive rollers, and thereafter optionally to a drying unit. The time spent by the sheet material in each vessel is determined by the transport speed and the dimensions of the vessel in the sheet feed path direction.
In a typical apparatus for liquid processing of photographic sheet material, a housing defines a treatment vessel having entrance and exit openings defining a sheet material path therethrough. The housing may include a collecting chamber positioned to collect treatment liquid which in use falls from the treatment vessel through the lower opening or through both of the openings, depending upon the orientation of the apparatus.
Usually, the treatment liquid collected in the collecting chamber is discarded. This is because exposure of the collected liquid to the atmosphere causes oxidation and/or evaporation of the liquid, and renders it less suitable for further use. However, such a practice is wasteful.
Where a vessel opening is closed by a pair of path-defining rollers biased into contact with each other to define a nip through which the sheet material path extends, it has been proposed to incorporate sealing devices between these path-defining rollers and the housing to reduce the quantity of liquid which falls through into the collecting chamber during use. The structure of such sealing devices can be complicated and costly, if the quantity of liquid falling into the collecting chamber is to be significantly reduced. United States patent U.S. Pat. No. 4,166,689 (Schausberger et al. assigned to Agfa-Gevaert AG) describes such an apparatus in which liquid escapes form the lower opening and is intercepted by the tank of a sealing device with two squeegees located in the tank above a horizontal passage in line with the lower opening. One or more pairs of drive rollers in the vessel close the lower opening and also serve to transport the sheet material along a vertical path which extends between the openings of the vessel.